Video Display Units: An Emission Source of the Contact Allergenic Flame Retardant Triphenyl Phosphate in the Indoor Environment H Å KAN CARLSSON, ULRIKA NILSSON, AND CONNY O ¨ STMAN* Department of Analytical Chemistry, Stockholm University, 106 91 Stockholm , Sweden Triphenyl phosphate, an additive flame retardant with documented contact allergenic effects on humans, was identified in a computerized indoor office environment. The source of emission was found to be the computer video display units (VDUs). Eighteen VDUs were examined, and the outer covers were shown to contain triphenyl phosphate in levels up to 10% (w/w). When using this type of PCequipment with a brand-new VDU in a small office room, the air concentration of triphenyl phosphate raised to near 100 ng/ m 3 after 1 day of operation. The measurements were performed in the breathing zone of an imaginary operator sitting in front of the computer. After 1 week of continuous operation, the concentration of triphenyl phosphate was reduced by half. Furthermore, a decrease to approximately 10 ng/m 3 could be observed after 183 days, which corresponds to more than 2 yr of ordinary business hour operation. Introduction Organophosphate esters, i.e., arylated, alkylated, or chloro- alkylated phosphate esters whose generalstructure is shown in Figure 1, are used on a large scale in the developed countries as flame retarding agents and/or plasticizers in a variety of products. Plastic materials, rubbers, varnishes, lubricants,hydraulicfluids,electronicgoods,such asTVsets and computers, often contain large quantities of added organophosphate esters. These additive flame retardant compounds are not covalently bound to the materials they are to protect.Theyare just mixed or dissolved in,for instance, the plastic polymer makingup the outer cover ofa computer VDU. Depending on its vapor pressure, the additive flame retardant may migrate out from the material and into the surrounding air. Organophosphate esters have been detected in indoor air (1-4). We have previously identified nine compounds of this class in common indoor environments, i.e., in school buildings, in a day care center, and in an office building (5). The compounds were found to originate from sources in the indoor environment. A wide range of biological effects of organophosphate esters has been reported (6-15). Triphenyl phosphate is widelyused as a plasticizer and flame retardant in electronic equipment. This compound is a potent inhibitor of human blood monocyte carboxylesterase (16) and has shown hemolytic toxicity (17). Furthermore, it has been demon- strated to cause contact dermatitis in humans (18-20). In the developed countries, computers can nowadays be considered as basic equipment in a common occupational office environment. Thus, ifcomputers contain and thereby emit organophosphate estersinto the surroundingair,a large part of the population is consequently exposed to these compounds.In the present study,our aim was to investigate occupational related computerized environments with re- spect to the occurrence and emission of commonly used flame retardants and/or plasticizers. Experimental Section Chemicals. Methanol (analytical grade, Merck, Darmstadt, Germany) was used without further purification, while acetone and dichloromethane were distilled in an all-glass apparatus prior to use. Triethyl, tri(n -propyl), tri(n -butyl), tri(2-chloroethyl), methyl diphenyl, triphenyl, tri(2-butoxy- ethyl), triethyl hexyl, and tritolyl phosphate were purchased from Aldrich Chemicals, Germany. Akzo Nobel, Sweden, kindly provided tri(chloropropyl) phosphate. A solution containing all 10 organophosphate esters was used as the external standard. Methyl diphenyl phosphate was used as an internalsurrogate standard and was added to the samples prior to the extraction procedure. Prior to GC analysis tri- (n -propyl) phosphate was added as an internal volumetric standard. All reference substances were of analytical grade (>98%), except for methyl diphenyl phosphate, which was oftechnical grade (80%). This chemical contained triphenyl phosphateasoneoftheimpurities.Byusingsemipreparative HPLC with an octadecylsilica column, it was possible to separate pure methyl diphenyl phosphate (99%) from the impurities. FTIR was used to ascertain that the obtained purified compound did not contain water. Cleaning Procedures. Our previous investigations have indicated that organophosphate estersare ubiquitousindoor air pollutants. We have also observed that all kind of laboratory utensils can be contaminated with organophos- phate esters. Thus, before use, all glassware was soaked in a solution of 5% (w/w) sodium hydroxide in ethanol for at least 12 h and then extensively rinsed with water, ethanol, and finallyacetone.The glassfiber filterswere ultrasonicated for 20 min in methanol, acetone, and dichloromethane, respectively. The PUFs were first boiled in water for 4 h in order to eliminate compounds containing nitrogen, such as isocyanates. They were then washed with water, acetone, and dichloromethane and finally Soxhlet-extracted for 12 h in dichloromethane (5). Sampling, Extraction, and Analysis. Two studies were performed in indoor office environments,i.e.,an intitialpilot *Corresponding author phone: +46 8 674 71 96; fax: +46 8 15 63 91; e-mail: conny.ostman@anchem.su.se. FIGURE 1. General structure of organophosphate esters. R1-R3 are either similar or different arylated, alkylated, or chloro-alkylated substituents. Environ. Sci. Technol. 2000, 34, 3885-3889 10.1021/es990768n CCC: $19.00  2000 American Chemical Society VOL. 34, NO. 18, 2000 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 3885 Published on Web 08/18/2000